摘要
苏鲁超高压带是否延伸到朝鲜半岛以及用何种方式延伸,成为很多地质学家注目的科学问题。新的研究成果包括:(1)在朝鲜半岛前寒武纪京畿陆块中,识别出一个含有榴辉岩的变质杂岩(洪城杂岩),榴辉岩透镜体出露于花岗片麻岩中,榴辉岩的锆石SHRIMP年龄是230Ma和～880Ma,围岩片麻岩的年龄约为810～820Ma;(2)朝鲜半岛的3个陆块(狼林、京畿和岭南陆块)具有与华北克拉通相似的岩石组合与演化历史;(3)南北朝鲜两个主要的古生代沉积盆地与华北具有很好的可比性;(4)临津江带和沃川带都不具有碰撞造山带的变质特征。据此提出了地壳拆离与逆冲模式,即华北与扬子陆壳的碰撞带沿朝鲜半岛西缘、大致呈南北走向分布。扬子陆壳俯冲带的深部(超高压部分)未在朝鲜半岛地表出露,下地壳(高压部分)从俯冲带拆离并逆掩到地表(洪城杂岩),以透镜体(岩片)状插入京畿地块的前寒武纪基底杂岩中,没有形成横穿朝鲜半岛的变质(造山)带。临津江带和沃川带有可能是扬子陆块的上地壳,它们从下地壳拆离、逆掩到地表,现在的展布状态是受到中生代构造的控制。
Considerable debate on whether and how the Sulu Orogenic Belt extends eastward to the Korean Peninsula has been lasting over the past decade. New results reported here include the following： （1） an eclogite and retrograded eclogite-bearing complex （Hongseong Complex） was discovered in South Korea, in which the eclogite occurs as lenses in ca. 810-820 Ma granitic gneiss. SHRIMP zircon dating of the eclogite yielded - 230 Ma for the metamorphic age and 880 Ma for the protolith age; （2） The basement of the Rangnim, Gyeonggi and Yeongnam massifs have affinities to the basement of the North China Block （NCB）. However, the Gyeonggi Massif encloses a minor amount of large or small slabs of the Hongseong Complex which is similar to the rocks of the Sulu Belt; （3） Two main Paleozoic basins within the Rangnim and Gyeonggi massifs have similar Paleozoic tectono-stratigraphy to the NCB; （4） The Imjingang and Ogcheon belts do not exhibit any metamorphic characteristics of collisional orogenic belts. Based on these facts, we propose a crustal-detachment and thrust model and suggest that the collision belt between the Yangtze Block （YB） and NCB （Sino-Korea Craton） is preserved along the western margin of the Korean Peninsula. The lower part of the UHP metamorphosed lithosphere of the YB was subducted under the Korean Peninsula and not exposed on the surface. The lower crust of the YB （the Hongseong Complex） was detached from the subducted lithosphere and thrust over the Korean Peninsula, and inserted into the basement rocks of the Gyeonggi Massif. The upper crust of the YB possibly was detached from the lower crust and overthrusted along the Honam and Chugaryong shear zones. The Imjingang and Ogcheon belts possibly represent the detached upper crust of YB and their present occurrences are controlled by a Mesozoic strike slip shear structure. All these detached lower and upper crustal slabs were strongly deformed during the Late Jurassic and Early Cretaceous tectonic event leading to their present geological distribution and characteristics.
出处
《高校地质学报》
CAS
CSCD
北大核心
2007年第3期415-428,共14页
Geological Journal of China Universities
基金
国家自然科学基金:(40672128
40421202)资助成果
